Carbureting apparatus



May19, 1942. L. E. PEI RRINE 2,283,694

CARBURETING APPARATUS Original Filed Sept. 25, 1955 Patented May 19, 1942 CARBURETING APPARATUS Lester E. Perrine, Detroit, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Substituted for abandoned application Serial No.

42,010, September 25, 1935. This application March 25, 1938, Serial No. 198,003

8 Claims. (01. 123-419) This invention relates to internal combustion engine carbureting apparatus.

The invention has to do principally with, although it is not applicable only to, carbureting apparatus which includes a pump which draws a current of air past a nozzle and reduces the pressure at the discharge end of the nozzle to such a value that liquid fuel is sprayed into the current of air and forms with it a combustible mixture which is forced into the cylinders of the engine by the pump.

The principal, but not the only, object of the invention is to provide in carbureting apparatus of the type described means which will enable the engine on which it is installed to idle properly at a predetermined low speed.

For a better understanding of the nature and objects of the invention, reference is made to the following specification in which there is described the preferred embodiment of the invention which is illustrated in the accompanying drawing.

The single figure of the accompanying drawing shows, mainly in section, carbureting apparatus in which my invention is embodied installed on a two-stroke cycle internal combustion engine.

The carbureting apparatus of the internal combustion engine I which is shown in the drawing includes a Venturi duct II whose outer end communicates with the atmosphere and whose inner end is connected to the intake side of a pump I2 of the type known as a Roots blower which may be driven from the crankshaft of the engine through a chain I3. The duct ll supports a constant level reservoir I4 to which liquid fuel is supplied through a pipe I5 and from which fuel may be delivered into the duct I l at the throat of the Venturi section through a nozzle l6.

To the discharge side of the pump I2, there is connected one end of a duct H. The other end of the duct I! may communicate directly with a single cylinder of the engine I 0 or with a number of cylinders of the engine through a manifold. In the duct N, there is located a butterfly type throttle valve I8 which is mounted on a shaft I9 to which there is connected an arm (not shown) through which the position of the valve may be changed to vary the effective area of the duct. To the duct I'I between the throttle valve I8 and the pump I2 and to the duct II near the pump, there are connected the opposite ends of a recirculating duct 20. In the recirculating duct, there is located a butterfly type valve 2| which is mounted on a shaft 22. The valve 2| is connected to the throttle valve I8, through an arm 23 which is fixed on the shaft 22, a link 24 and an arm 25 which is fixed on the shaft I9, so that it is closed as the throttle valve is opened and opened as the throttle valve is closed. In the recirculating duct 20, there is also located a poppet valve 26 which is urged toward its closed position by a spring 21 and is moved toward its open position when the valve 2| is open and the pressure in the duct I1 exceeds that in the duct II by a predetermined amount.

If carbureting apparatus constructed in accordance with the foregoing portion of this specification is designed so that it will supply the maximum demands of the engine In and furnish theengine with a combustible mixture which contains the desired proportions of fuel and air when it is operating at moderate speeds, it will be defective in twoparticulars, viz., (1) it will not idle the engine properly, i. e., smoothly at a uniform low speed, because when the throttle valve I8 is closed to a satisfactorily low idle speed position the rate of flow of air through the duct II falls to such a small value that insuflicient fuel to carburet it adequately is discharged from the nozzle I6 and the inevitable variations in the pressure within the duct I1 between the pump I2 and the throttle valve [8 are directly reflected in the rate of introduction of carbureted air into the engine and (2) it will supply the engine with an undesirably rich combustible mixture when it is operating at very high speeds. t?

To eliminate the last mentioned defect, I provide in the duct I I between the nozzle I6 and the pump I2 an orifice 28 and a poppet valve 29 which is urged to the position in which it closes the orifice by a spring 30. When the engine is operating at low or moderate speeds, the valve 29 is held in the position in which it closesthe orifice 28 by the spring 30. But when the engine is operating at extremely high speeds, the suction within the duct II opens the valve 29 against the resistance of the spring 30 and sufficient air to reduce the richness of the combustible mixture supplied to the engine to the desired extent is, consequently, admitted into the duct II through the orifice 28.

To make the engine II] idle properly, I provide a recirculating tube 3| which connects the portion of the duct I! on the atmospheric side of the throttle valve I8 with theportion of the duct II on the. atmospheric side of the nozzle I6 and, preferably in the wall of the duct IT, a tubular passage 32 which interconnects the portions of recirculating tube 3I maintains the ratio of fuel to air in the mixture of fuel and air which enters the engine at the proper value when the throttle valve is closed.

To explain how the passage 32 with the Venturi section 34 in it effects the result ascribed to it) I point out that the throttle valve I8 is fitted so that when it is closed carbureted air can enter the engine only through the passage 32 and that the Venturi section 34 is so designed that its critical pressure is below that which exists in the duct IT on the atmospheric side of the throttle valve when the throttle valve is closed and only sufficient combustible mixture to enable the engine to idle at the desired speed can enter it through it.

To explain how the recirculating tube 3| effects the result ascribed to it, I point out that when the throttle valve I8 is closed some of the combustible mixture in excess of that required by the engine is conducted by the recirculating tube from the duct IT on the atmospheric side of the throttle valve I8 into the duct II on the atmospheric side of the fuel nozzle 6 whence, with some uncarbureted air from the atmosphere, it is returned by the pump I2 to the duct I1, The uncarbureted air drawn from the atmosphere into the duct II by the pump I2 is thus, without reduction of the rate of flow of air past the nozzle I6, reduced to a volume that the fuel discharged from the nozzle I6 is sufiicient to carburet adequately.

As the throttle valve I8 is opened, the rate of discharge of fuel from the nozzle I6 increases more rapidly than the rate of fiow of air through the duct I I and less and less and finally no combustible mixture from the recirculating tube 3| is needed to maintain the ratio of fuel to air in the combustible mixture which enters the engine at the proper value. To prevent the combustible mixture which enters the engine becoming too rich by reason of this circumstance, there is preferably provided means to decrease the volume of combustible mixture fed into the duct I I through the recirculating tube as the throttle valve is opened. The poppet valve 35 which is urged toward its closed position by a spring 36 serves this purpose. A finger 31 which is pivotally mounted on the engine I0 is connected to the arm on the throttle valve shaft I9 by a link 38 so that it engages under a head 39 on the stem of the valve 35 and holds it open when the throttle valve is closed but'moves downwardly and permits the spring 36 to move the valve toward its closed position as the throttle valve is opened and to its closed position by the time that the throttle valve is opened to the position in which no combustible mixture from the recirculating tube that no more combustible mixture than the maximum required can be fed into the duct II through the recirculating tube at any time the valve 35 is open and a vent 40 through which combustible mixture may be discharged into the atmosphere from the recirculating tube if the introduction of all of it into the duct I I produces a too rich combustible mixture. To regulate the vent 40 a screw 4| is provided.

It will, of course, be understood that although the carbureting apparatus herein disclosed was primarily designed for use on a two-stroke cycle engine, it may be employed on engines of other types.

. This application is a substitute for my application, Serial No. 42,010, which was filed on September 25, 1935.

I claim:

1. Internal combustion engine carbureting apparatus which includes a duct for conducting air from the atmosphere to the engine, a blower for moving air through the duct from the atmosphere to the engine, means through which fuel may be introduced into the duct, a valve for regulating the passage of combustible mixture from the carbureting apparatus to the engine, a passage for conducting combustible mixture from the engine side to the atmospheric side of the blower and the specified means, and a valve for regulat-' ing the passage of combustible mixture from the engine side to the atmospheric side of the blower and the specified means connected to the first specified valve so that it is closed when the first specified valve is opened and opened when the first specified valve is closed.

2. Internal combustion engine carbureting apparatus which includes a duct for conducting air from the atmosphere to the engine, a blower for moving air through the duct from the atmosphere to the engine, means through which fuel may be introduced into the duct, a passage for conducting combustible mixture from the engine side to the atmospheric side of the blower and the specified means, and a vent in the passage through which combustible mixture may be discharged into the atmosphere from it,

3. Internal combustion engine carbureting apparatus which includes a duct for conducting air from the atmosphere to the engine, a blower for moving air through the duct from the atmosphere to the engine, means through which fuel may be introduced into the duct, a valve for regulating the passage of combustible mixture from the carbureting apparatus to the engine, a passage for conducting combustible mixture from the engine side to the atmospheric side of the blower and the specified means, a valve for regulating the passage of combustible mixture from the engine side to the atmospheric side of the blower and the specified means connected to the first specified valve so that it is closed when the first specified valve is opened and opened when thefirst specified valve is closed, and flow limiting means in the passage.

l. Internal combustion engine carbureting apparatus which includes a'duct for conducting air from the atmosphere to the engine, a blower for moving air through the duct from the atmosphere to the engine, means through which fuel may be introduced into the duct, a valve for regulating the passage of combustible mixture from the carbureting apparatus to the engine, a passage for conducting combustible mixture from the engine side to the atmospheric side of the blower and the specified means, a valve for regulating the passage of combustible mixture from the engine side to the atmospheric side of the blower and the specified means connected to the first specified valve so that it is closed when the first specified valve is opened and opened when the first specified valve is closed, a venturi in the passage for limiting the fiow of combustible mixture through it, and a vent in the passage through which combustible mixture may be discharged into the atmosphere from it.

5. Internal combustion engine carbureting apparatus which includes a duct for conducting air from the atmosphere to the engine, a blower for moving air through the duct from the atmosphere to the engine, means through which fuel may be introduced into the duct on the atmospheric side of the blower, a valve on the engine side of the blower for regulating the passage of combustible mixture from the carbureting apparatus to the engine, a passage for conducting combustible mixture from the duct between the blower and the specified valve to the duct on the atmospheric side of the specified means, and a valve for regulating the passage of combustible mixture from the duct between the blower and the specified valve to the duct on the atmospheric side of the specified means connected to the first specified valve so that it is closed when the first specified valve is opened and opened when the first specified valve is closed.

6. Internal combustion engine carbureting apparatus which includes a duct for conducting air from the atmosphere to the engine, a blower for moving air through the duct from the atmosphere to the engine, means through which fuel may be introduced into the duct on the atmospheric side of the blower, a valve on the engine side of the blower for regulating the passage of combustible mixture from the carbureting apparatus to the engine, a passage for conducting combustible mixture from the duct between the blower and the specified valve to the duct on the atmospheric side of the specified means, a valve for regulating the passage of combustible mixture from the duct between the blower and the specified valve to the duct on the atmospheric side of the specified means connected to the first specified valve so that it is closed when the first specified valve is opened and opened when the first specified valve is closed, and fiow limiting means in the passage.

7. Internal combustion engine carbureting apparatus which includes a duct for conducting air from the atmosphere to the engine, a blower for moving air through the duct from the atmosphere to the engine, means through which fuel may be introduced into the duct, a valve for regulating the passage of combustible mixture from the carbureting apparatus to the engine, a passage forconducting fluid from'the atmospheric to the engine side of the specified valve when it is closed, a passage for conducting combustible mixture from the engine side to the atmospheric side of the blower and the specified means, and fiow limiting means in the first specified passage.

8. Internal combustionengine carbureting apparatus which includes a duct for conducting air from the atmosphere to the engine, a blower for moving air through the duct from the atmosphere to the engine, means through which fuel may be introduced into the duct on the atmospheric side of the blower, a valve on the engine side of the blower for regulating the passage of combustible mixture from the carbureting apparatus to the engine, a passage for conducting combustible mixture from the atmospheric to the engine side of the specified valve when it is closed, a venturi in the passage for limiting the fiow of combustible mixture through it, a passage for conducting combustible mixture from the duct between the blower and the specified valve to the duct on the atmospheric side of-the specified means, a valve for regulating the passage of combustible mixture from the duct between the blower and the specified valve to the duct on the atmospheric side of the specified means connected to the first specified valve so that it is closed when the first specified valve is opened and opened when the first specified valve is closed, and a venturi in the passage for limiting the fiow of combustible mixture through it.

LESTER E. PERRINE. 

